When sowing crops such as maize, sunflowers and soya beans, it is desirable to plant, in each row, single seeds at a predetermined distance from each other. In order to achieve this, a so-called precision seeder, or “planter”, can be used. A precision seeder can comprise a seed hopper, a seed distributing device, a seed feeding tube, a seed furrow opener, a seed knife, a press wheel and a seed furrow covering means.
An example of a seed distributing device for a precision seeder is disclosed in U.S. Pat. No. 4,047,638. This precision seeder has what is generally referred to as a singulating disc, i.e. a disc that rotates in a cavity where, on one side of the disc, there is an excess pressure and on the other there is a normal pressure. On the excess-pressure side, seeds are supplied from a seed hopper, so that the lower portion of the disc moves through a bulk quantity of seeds. By providing the disc with a number of perforations or holes, through which only air and not seeds is able to pass, the seeds will be “sucked” tight to the holes and lifted out of the bulk quantity of seeds. In another portion of the cavity, the hole can be temporarily obstructed on the normal-pressure side, thus causing the seed to fall by gravity from the disc and into a seed feeding tube through which it is conveyed to the seed knife.
It is desirable to position the singulating disc inside a seed housing so as to protect it from external damage.
To optimize the ability of the singulating disc to single out and retain seeds, it is desirable to establish a definite and stable pressure difference between the excess-pressure side of the singulating disc and its normal-pressure side, given an existing air flow and pressure.
To permit the use of one and the same seeder for several different types of crop, simple switching between different singulating discs is desirable, so that crop of different seed size can be sowed and/or seeds can be planted at different distances.
Thus, a number of challenges remain as regards the designing of a seed housing for a precision seeder.